Patent GB-1290042-A (GB)
IPC: G06K9/64
Filed: 1970-08-25
Abstract: 1290042 Character recognition INTERNATIONAL STANDARD ELECTRIC CORP 25 Aug 1970 [29 Aug 1969] 40821/70 Addition to 1227120 Heading G4R The character recognition apparatus of the parent is modified by use of intermediate storage and alteration of the contrast of "shape"  elements in dependence on the number of occurrences of a "shape" element. A matrix decomposition of a character scanned by a column of photo-cells (each point preferably quantized to four levels) in a shift matrix is shifted out vertically to a second shift matrix from which it can be applied repetitively, one row in parallel at a time, via a correction network to a correlation matrix. Each such application of the character is for a respective recognition attempt. Four attempts are made (or as a modification, up to four attempts, stopping on successful recognition). For the four attempts respectively, the correction network (a) passes its input unchanged, (b) brightens rows in response to the majority of several adjacent rows being too dark, (c) darkens rows if similarly too bright, (d) removes small dark spots surrounded by white. Necessity of correction is indicated in response to a row of the second shift matrix, particular intensity values being decoded by gates. For (b), the decoding gates control resistor adders feeding comparators feeding a counter via an AND gate, the counter stages feeding a trigger acting as a thresholder, via a resistor adder. For (c), the decoding gates feed a counter via an AND gate, the counter stages feeding a thresholder trigger via a resistor adder. For (d), the decoding gates feed shift registers, the stages of which feed gates. The actual correction is done by converting each point value from binary to a 1 -out-of-4 marking, altering it in gates, and converting it back. As in the parent, the highest output from the correlation matrix in response to each application of a row of the character is detected and, in dependence on the current vertical zone of the character, used to increment each one of n counters (n = number of possible characters) which corresponds to a character having that row at that vertical zone. However, the counters add together the results from the four recognition attempts, the largest count finally providing a first version of the character identity. A further n counters, fed similarly, are provided in parallel, but the largest count is determined after each recognition attempt, to increment the corresponding one of another n counters. The largest count of these latter counters is finally determined to give a second version of the character identity. The two versions are compared to give the final identity if equal. Each highest output of the correlation matrix (see above) is converted into a pulse on one of 32 lines to feed the counters in accordance with the zones, but 4 of these lines also feed respective 4-stage shift registers, 2 or 3 stages of each of which supply a voltage to the corresponding rows of the correlation matrix via resistor adders (one connected to each register) to improve contrast for noise reduction. Each row of the correlation matrix has two row lines feeding a respective differential amplifier, the voltage being applied to one line in the ease of two rows and the other in the case of the other two rows. Columns 1-5 and 2-6 of the second shift matrix may be applied in turn to the correlation matrix for respective recognition attempts to compensate for displacement, or the two sets of columns may be applied simultaneously. In the simultaneous case, corresponding pulses for the two cases are ORed prior to the zone gating or alternatively after detection of the largest count (in which case twice as many counters are needed). A counter incremented by appearance of the character at the top (output) of the second shift matrix defines the recognition attempts to control the correction network.